1. Field of the Invention
The present invention relates to a head supporting mechanism for supporting a recording/reproduction use head that makes an access to a recording medium in an information recording apparatus.
2. Description of the Related Art
A head for recording/reproducing data on and from an information recording medium in an information recording apparatus such as a magnetic disk apparatus is installed on a slider that allows the head to float over the recording medium with a fine gap in between. A head supporting mechanism is used for supporting this head slider. The head supporting mechanism is attached to an actuator arm that is driven by a voice coil motor (VCM) serving as a driving source.
A suspension arm is attached to the actuator arm that is driven by the voice coil motor so as to freely pivot thereon, and the head slider is attached to the suspension arm. A fine-movement actuator utilizing a thin-film piezoelectric element is interpolated between the actuator arm and the suspension arm so that the suspension arm is allowed to pivot by driving the fine-movement actuator, thereby allowing the head on the slider to land on a track.
Great shifts such as a seeking operation of the head slider are carried out by controlling the voice coil motor, and the tracking compensation for landing-on a track is carried out by controlling the fine-movement actuator.
However, recent developments of high recording density in recording media and the resulting high-speed rotation of the recording medium have taken place so fast that it is sometimes difficult for the head supporting mechanism of the above-mentioned arrangement to follow the developments.
In the case of the head supporting mechanism having the above-mentioned arrangement, the entire suspension arm including the head slider is driven by the fine-movement actuator. However, the suspension arm is considerably long, and has a great mass with a great moment of inertia. For this reason, in the tracking compensation for positioning the head on a target track when the head is lifted off track, it is difficult to properly provide a high-speed response with high precision.
Therefore, the main objective of the present invention is to provide a head supporting mechanism of an information recording apparatus that can achieve a high-speed responding property and a high-precision positioning control in the tracking compensation for a target track.
Another objective of the present invention is to provide a head supporting mechanism that can improve the floating characteristic of the slider with respect to the recording medium.
Still another objective, feature and advantage of the present invention will be clarified by the following description.
In order to solve the above-mentioned subjects, the present invention relating to the head supporting mechanism is provided with the following means.
A slider-supporting beam is attached to an actuator arm that shifts relative to a recording medium. A slider supporting member is supported on a free end of the slider supporting beam so as to freely rotate thereon. A displacement member is connected to the slider supporting member, and based upon the operation of the displacement of the displacement member, the slider supporting member is allowed to pivot around the pivotal center together with the slider placed thereon. The displacement member is directly or indirectly attached to a slider supporting beam. The connecting point of the displacement member and the slider supporting member is placed at a position different from the pivotal center so that the displacement of the displacement member allows the slider supporting member to pivot around the pivotal center.
In other words, the head supporting mechanism of the present invention is provided with a slider on which a head for recording and reproducing data on and from the recording medium is installed, a slider supporting member for supporting the slider, a slider supporting beam the base side of which is attached to the actuator arm and the free end of which is provided with the slider supporting member so as to freely pivot thereon, and a displacement member which makes a displacement so that the slider supporting member is allowed to pivot together with the above-mentioned slider.
Here, the relative shifts of the actuator arm may be provided as rocking movements or linear shifts.
In accordance with the above-mentioned arrangement, the displacement member is operated so that the slider supporting member supporting the slider is allowed to pivot around the pivotal center with respect to the slider supporting beam. The slider is allowed to pivot together with the slider supporting member.
In the case when the slider supporting beam is connected to the actuator arm so as to freely pivot thereon and the entire portion of the slider supporting beam is allowed to pivot, the slider supporting beam including the slider that is to pivot has a greater mass. Moreover, the length of the slider supporting beam that corresponds to an effective radius of the displacement of the slider is greater. Therefore, when the slider supporting beam is allowed to pivot so as to make a displacement of the slider, a delay in response may occur.
In contrast, in the present invention, the slider supporting member is allowed to pivot around the pivotal center within the area range of the slider supporting member itself. The pivotal centers of the slider and the slider supporting member that are the subjects of the pivot need not be coincident with the center of gravity of the slider; however, they are certainly placed within the area of the slider supporting member. The slider supporting member is supported within the area range so as to freely pivot therein so that the effective radius of the pivot is sufficiently small as compared with the case in which the slider supporting beam is allowed to pivot. Moreover, the subjects of the pivot are the slider and the slider supporting member, and their masses are smaller than the mass of the slider supporting beam containing the slider. The moment inertia of the two members, that is, the slider and the slider supporting member, is smaller than the moment inertia of the three members, that is, the slider, the slider supporting member and the slider supporting beam; therefore, it is possible to set smaller the driving torque of the slider and the slider supporting member caused by the operation of the displacement member. Moreover, since they have a small dimension and light weight, it is possible to improve the response characteristic and precision in the tracking compensation for positioning to a target track when the head has a positional deviation from the target track. In other words, the present invention makes it possible to provide a head supporting mechanism of an information recording apparatus which can make a fine displacement on the head with high precision at high speeds.
In a preferred embodiment of the above-mentioned head supporting mechanism, the pivotal center at which the slider supporting member is supported to freely pivot thereon by the slider supporting beam is set to a position corresponding to the center of gravity of the slider or the vicinity thereof.
The displacement of the displacement member allows the slider supporting member to pivot around the pivotal center together with the slider; and in this case, when the pivotal center is set at the position of the center of gravity of the slider, it is possible to smoothly carry out the pivotal movement of the slider caused by the displacement of the displacement member.
In another preferred embodiment of the above-mentioned head supporting mechanism, a pair of the above-mentioned displacement members are placed in a symmetric manner. The pair of displacement members are placed symmetrically with respect to the center line along the length direction of the slider supporting beam passing through the center of rotation of the slider supporting member. Moreover, either one of the paired displacement members is extended, with the other being contracted, so that they are allowed to carry out respective operations in directions opposite to each other.
This is a translational arrangement of a link mechanism, and with respect to the operations for allowing the slider to pivot together with the slider supporting member around the pivotal center, the pivotal operation in the clockwise direction and the pivotal operation in the counterclockwise direction are made equivalent to each other. In addition, both of the pivotal operation in the clockwise direction and the pivotal operation in the counterclockwise direction allow the pivotal movement of the slider to become more smoother. Here, with respect to the translational link mechanism, a pair of displacement members are not necessarily set in parallel with each other.
In still another preferred embodiment of the above-mentioned head supporting mechanism, the slider supporting beam is formed as a load beam having an elasticity, and this load beam and the slider supporting member are connected to each other through a flexure that is a flexible wiring substrate for providing wiring to the head in the slider, and a protrusion placed on the free end of the load beam is allowed to contact the slider supporting member so that the above-mentioned protrusion supports the slider supporting member so as to freely pivot thereon centered on the protrusion serving as the pivotal center.
The slider supporting beam is designed as a load beam having an elasticity. The flexure is secured to the load beam with one portion thereof being not secured, a slider supporting member is attached to the portion of the flexure that is not secured. The protrusion on the free end of the load beam presses the slider supporting member attached to the flexure toward the recording medium, thereby applying a load thereon.
The slider, which faces the surface of the recording medium rotating at a high speed, is allowed to float by a pressure caused by air currents generated on the surface of the recording medium. Even when the surface of the recording medium has a waved form, the flexure and load beam are properly combined so that the fine gap distance between the slider and the recording medium is maintained at a predetermined range. In other words, it is possible to improve the floating characteristic of the slider.
In a preferred embodiment of the above-mentioned arrangement, the displacement member is formed by a thin-film piezoelectric element, and this thin-film piezoelectric element is bonded to the flexure. The thin-film piezoelectric element is fine in dimension, the thickness is sufficiently thin with a sufficiently light weight, and the operational characteristic in extension and contraction at the time of the voltage control is stable. By bonding the thin-film piezoelectric element to the flexure, it is possible to easily arrange the displacement member in the vicinity of the slider supporting member.
In a preferred embodiment in the above-mentioned arrangement, in the above-mentioned flexure, at two portions that are symmetrical with respect to the center line along the length direction of the load beam passing through the protrusion of the load beam, a pair of elastic hinge portions, each having a necked shape, are formed. In this case, with respect to the displacement member, it does not make any difference whether or not it is provided as the thin-film piezoelectric element.
The slider supporting member is attached to a flexure portion closer to the free end than to the paired elastic hinge portions. The paired displacement members are connected to the slider supporting member attached to the flexure portion on the free end side through the pair of elastic hinge portions.
The slider supporting member, attached to the flexure through the pair of elastic hinge portions, that is, the slider, is allowed to have a flexible state in each of the pitching direction and the rolling direction, that is, the degree of freedom in both of the directions. Therefore, even when the recording medium rotating at a high speed has a waved surface, it is possible to provide a superior floating characteristic of the slider with respect to the surface of the recording medium.
It is essential to allow the yawing of the slider to make a high-speed in response to the tracking compensation while maintaining the free pitching and rolling states of the slider.
One of the displacement members is extended, while the other displacement member is contracted. On the extended side, the elastic hinge portion is pushed out toward the free end so that the slider supporting member is displaced around the pivotal center. The transmission of this displacement is alleviated by the elastic hinge portion on the contracted side, with the result that the operating force of the displacement is not transmitted to the displacement member on the other extended side.
Moreover, on the contracted side, the elastic hinge portion is pulled back to the base side, thereby allowing the slider supporting member to be displaced around the pivotal center. The transmission of this displacement is alleviated on the elastic hinge portion on the extended side, with the result that the active force of the displacement is not transmitted to the displacement member on the other extended side.
Therefore, the pair of displacement members allow virtually only the flexure portion that is closer to the free end side than to the pair of elastic hinge portions to pivot around the pivotal center, with the mutual symmetrical relationship being maintained. In other words, the operations of the extension and contraction of the pair of displacement members, that is, the extension of one of the members and the contraction of the other member are smoothly achieved, without causing any interference from each other. Consequently, it is possible to allow the slider to smoothly pivot with less resistance by using a smaller driving force. Moreover, the tracking compensation for the head is achieved at high speeds with high precision, with less response delay.
In a preferred embodiment in the above-mentioned arrangement, the pair of elastic hinge portions are placed on a straight line in a right angle direction with respect to the center line of the load beam, which passes through the protrusion on the load beam. In this case, it is possible to transmit the driving force of the displacement member more effectively. If the pair of elastic hinge portions are placed so as to be separated from the straight line passing through the protrusion, mismatching will occur with respect to the active force transmission, causing a reactive force and the subsequent beating phenomenon in the load beam. When it is placed on the straight line passing through the protrusion, such reactive force and beating phenomenon are not generated. Therefore, it is possible to provide the high-speed response property and high-precision positioning property more effectively.
In a more preferable embodiment in the above-mentioned arrangement, a pair of thin-film piezoelectric elements are symmetrically placed as the displacement members. The pair of thin-film piezoelectric elements are symmetrically placed with respect to the center line along the lengthwise direction of the load beam, which passes through the protrusion forming the rotation center in the load beam. The pair of thin-film piezoelectric elements are bonded to a flexure. The pair of thin-film piezoelectric elements are allowed to extend and contract in the mutually reversed directions so that either one of the pair of thin-film piezoelectric elements is extended with the other being contracted. With this translational arrangement of the link mechanism in the thin-film piezoelectric elements, the pivotal movement of the slider in any of the clockwise direction and the counter clockwise direction is made equivalent to each other, and is also made smoother.
In a preferable embodiment in the above-mentioned arrangement, the slider supporting member is supported so as to freely pivot on the position of the center of gravity of the entire subject of the pivotal movement consisting of the slider and the slider supporting member. If the subject of the pivotal movement is supported so as to freely pivot on a position apart from the center of gravity, a moment corresponding to the radius from the pivotal center and the center of gravity is generated, thereby causing a reactive force on the pivotal center. This reactive force reversely acts on the pair of displacement members, thereby returning the subject of the pivotal movement in the reversed direction. This causes a response delay in the tracking compensation. By making the fulcrum of the pivotal movement and the center of gravity of the pivotal movement coincident with each other, it becomes possible to prevent the generation of the reactive force, and consequently to more effectively transmit the driving force of the displacement member. Therefore, it is possible to provide the high-speed responding property and the high-precision positioning operation more effectively.
In a preferable embodiment in the above-mentioned arrangement, the slider supporting member is constituted by a main section to be connected to the flexure and a slider center-of-gravity holding section. The slider center-of-gravity holding section is formed in a manner so as to connect to the main section for the connection to the flexure, thereby allowing the protrusion on the load beam to contact as well as fixing the slider in its center of gravity or in the vicinity thereof.
The protrusion on the free end of the load beam supports the slider on its center-of-gravity or in the vicinity thereof through the slider center-of-gravity holding section of a slider supporting member, and also provides the center of the pivotal movement to the slider. Thus, the relative orientation angle of the slider with respect to the load beam, in particular, the setting of the inclination in the pitching direction, can be accurately achieved by simple methods, that is, the adjustments of the protruding amount of the protrusion and the dimension of the slider center-of-gravity holding section.
The relative inclination in the pitching direction of the slider with respect to the recording medium is determined in various manners depending on the specifications in the information recording apparatus. In response to each of the variations, not an arrangement in which each of all the constituent elements is modified so as to be applied to each specification, but an arrangement in which the load beam and slider are set as commonly-used components and the dimension of the slider center-of-gravity holding section is adjusted in the slider supporting member is utilized. In other words, the setting of the relative inclination in the pitching direction in the slider with respect to the recording medium is easily carried out, thereby making it possible to provide a superior floating characteristic of the slider.
In a preferable embodiment in the above-mentioned arrangement, the above-mentioned slider supporting member is provided with a mass balancing section for balancing the mass of the main section with respect to the slider center-of-gravity holding section, in addition to the main section and the slider center-of-gravity holding section.
In the flexure, the slider supporting member is attached to the free end side as compared with the elastic hinge portion; and in order to provide a preferable floating characteristic for the slider, the slider supporting member needs to be set free from the portion to which the thin-film piezoelectric element is bonded in the flexure. However, in contrast, the slider supporting member is preferably arranged so as to support the slider on its center of gravity. In this case, without any modification, the shape of the slider supporting member would cause degradation in the entire mass balance with respect to its slider center-of-gravity holding section. This arrangement is made because in the flexure, it is not preferable to make the slider supporting member in contact with the portion to which the thin-film piezoelectric element is added.
For this reason, the above-mentioned mass balancing section is installed so as to provide a well-balanced mass as a whole. The protrusion on the load beam supports the slider supporting member on its center of gravity, and also indirectly supports the slider on its center of gravity or on the vicinity thereof. In other words, the entire portion of the subject of the pivotal movement including the slider supporting member and the slider can be supported in a well-balanced manner; therefore, it is possible to improve the floating characteristic of the slider in both of the pitching direction and the rolling direction.
In a preferable embodiment in the above-mentioned arrangement, the above-mentioned slider center-of-gravity holding section has an arrangement in which a portion extending integrally from the main section of the slider supporting member is formed by a bending process. Thus, it is possible to simplify the structure for easily setting the inclination of the slider in the pitching direction.
Moreover, in a preferable embodiment in the above-mentioned arrangement, the above-mentioned slider center-of-gravity holding section is formed by integrally molding it together with the molding process of the wiring-use flexible substrate of the flexure. Thus, it is possible to provide a smooth yawing operation of the slider while maintaining a sufficient degree of freedom in the pitching operation and the rolling operation of the slider. It is also possible to easily form the slider center-of-gravity holding section.
In a preferable embodiment in the above-mentioned arrangement, the above-mentioned pair of elastic hinge portions are placed within a slider area range when viewed in the stacking direction of the slider and the slider supporting member.
In the case when a pair of elastic hinge portions are placed outside the slider area range, the distance from the pivotal center to the elastic hinge portion is long. The angle in which the slider is allowed to pivot is small with respect to an extension or a contraction at a fixed dimension of the displacement member. In the case when the angle xcex8 is minute, if xcex8 is represented by a radian unit, the following equation is satisfied with respect to a minute deviation xcex5 in the displacement member in the radius r from the pivotal center.
xcex8=xcex5/r 
Thus, the smaller the radius r, the greater the pivotal angle xcex8. By placing the pair of the elastic hinge portions within the slider area range, it is possible to make the pivotal angle of the slider greater with respect to a fixed displacement of the displacement member. Consequently, it is possible to improve the responding property in the tracking compensation.
Here, in the case when a pair of elastic hinge portions are placed within the area range of the slider, the arrangement of the above-mentioned mass balancing portion becomes more beneficial.
In a preferable embodiment of the above-mentioned arrangement, the thin-film piezoelectric member is constituted by a plurality of piezoelectric elements that are stacked, with the voltage-applying directions of the plurality of thin-film piezoelectric elements being set opposite to each other.
In this case, in comparison with a single-layered thin-film piezoelectric member, it is possible to provide a sufficient power for allowing the slider to pivot for the tracking compensation. Moreover, it is possible to prevent warping due to bimorph and consequently to extend and contract the thin-film piezoelectric member within the in-plane of the original film in a manner of parallel displacement. In the case of a single layer, a warp is generated. Even in the case of a plurality of layers, a warp is generated in each layer; however, by reversing the respective voltage-applying directions, the directions of the warps are made opposite to each other so as to cancel the warps as a whole. By restricting the wasteful movement of the warp, it becomes possible to effectively utilize the extending and contracting energy, and consequently to improve the responding property of the tracking compensation.
In a preferable embodiment in the above-mentioned arrangement, with respect to the application of a voltage to the pair of thin-film piezoelectric members, a bias voltage is applied in its initial conditions, and based upon this bias voltage, voltages having mutually reversed polarities are applied in its extending and contracting operations.
In this case, the length of the thin-film piezoelectric member with a bias voltage being applied is determined as a reference. In other words, a voltage to be applied to both of the thin-film piezoelectric members when the head is landed on a target track is a bias voltage. Depending on cases in which a voltage higher than the bias voltage and a voltage lower than the bias voltage are applied, the extending and contracting operations are set symmetrical with each other.
When the head is dislocated from the target track, a tracking compensation control operation is carried out. When the head is dislocated in the right direction from the target track, it is returned to the left direction; however, it is difficult to allow the head to land directly on the target track by using only this operation. Due to an overshoot, this time, the head is dislocated in the left direction from the target track. At this time, the head is returned in the right direction. In other words, alternate movements are carried out. In this case, the directions of voltages to be applied to the pair of thin-film piezoelectric members are also alternately changed. Therefore, when voltages in the reversed polarities are applied based upon the bias voltage, the extending and contracting operations are set symmetrical with each other, thereby making it possible to quickly carry out the reducing process of the hunching due to the overshoot. As a result, controlling operations of the extending and contracting operations in the thin-film piezoelectric members are carried out at high speeds with high precision.
In a preferable embodiment in the above-mentioned arrangement, wires in the above-mentioned flexure are placed along the end edges of the flexure on both of the outsides of the thin-film piezoelectric member that is bonded to the flexure. Thus, the strength of the flexure is increased by the wires so that it becomes possible to prevent the flexure from warping due to the extending or contracting thin-film piezoelectric member, and consequently to effectively transmit the extending or contracting force of the thin-film piezoelectric member to the slider supporting member.
In a preferable embodiment in the above-mentioned arrangement, the above-mentioned flexure and the thin-film piezoelectric member are arranged so that neutral axes on the center in the thickness direction of the two members are set to be virtually coincident with each other.
When voltages in the reversed polarities are alternately applied to the thin-film piezoelectric member, the corresponding vibrations are generated in the flexure. These vibrations take place in the normal direction with respect to the surface of the flexure. In this case, when the neutral axis of the flexure and the neutral axis of the thin-film piezoelectric member have a step difference in the normal direction, the step difference dimension is allowed to form the arm of a moment. Then, the vibration of the flexure is amplified through the arm, resulting in a phenomenon in which the elastic hinge portion is vibrated. This phenomenon causes an unnecessary movement in the pitching direction in the slider.
Therefore, by making the neutral axis of the flexure (elastic hinge) and the neutral axis of the thin-film piezoelectric member coincident with each other, the arm of the moment is eliminated so that even when the flexure is vibrated, the amplification thereof is suppressed. Consequently, it is possible to control the tracking compensation at high speeds, with high precision.
In a preferable embodiment in the above-mentioned arrangement, the thin-film piezoelectric member is coated with a protection member. Thus, the thin-film piezoelectric member is protected and the thickness of the thin-film piezoelectric member is increased so that it is possible to suppress the warp of the thin-film piezoelectric member and also to provide a more effective operation of the slider pivotal movement caused by the extension and contraction of the thin-film piezoelectric member.
In a preferable embodiment in the above-mentioned arrangement, a wire is allowed to pass through the pair of elastic hinge portions. Here, the thickness of the wire passing through the elastic hinge section is set to be greater than the width thereof. This portion of the flexure, which has a necked shape, is also used as the elastic hinge portion and the line passage portion. Further, this essential thin portion having the necked shape is reinforced so as to improve the reliability.
Here, with respect to information recording apparatuses to which the above-mentioned head supporting mechanism is applied, apparatuses such as a magnetic disk apparatus, an optical disk apparatus and a magneto-optical disk apparatus, are listed.